return fmt.Errorf("Error switching to ns fd %v: %v", n.Fd(), err)
	}
	return nil
}

// inspired by netns.Do() but with an existing fd.
func NetnsDo(fdable NetnsFd, toRun func() error) error {
	containedCall := func() error {
		threadNS, err := netns.GetCurrentNS()
		if err != nil {
			return fmt.Errorf("failed to open current netns: %v", err)
		}
		defer threadNS.Close()

		// switch to target namespace